ASTR101: Introduction to Astronomy

Unit 5: Matter and LightIn this unit, you will be introduced to some basic physics that is used
to describe the universe. The most obvious components of the physical
universe are matter and light, though it turns out to be a bit more
complicated than that. Matter is composed of atoms, which, for our
purposes, will be described by the Bohr model. We now know that light
is just part of a larger phenomenon known as electromagnetic radiation.
The physics of this unit will be the basis for the later units on the
evolution of the universe from its beginning to the present.

Unit 5 Time Advisory
This unit should take approximately 13 hours to complete.

☐ Subunit 5.1: 3 hours

☐ Subunit 5.2: 1 hour

☐ Subunit 5.3: 2 hours

☐ Subunit 5.4: 2 hours

☐ Subunit 5.5: 2 hours

☐ Subunit 5.6: 1 hour

☐ Assessment: 2 hours

Unit5 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- List the advances in our knowledge of the atom from the time of
Democritus to the present.
- Compare and contrast the Bohr model of the atom to earlier models.
- Compare and contrast the differences between the wave and particle
models for light and list the nineteenth-century evidence in favor
of the wave model.
- List the major divisions of the electromagnetic spectrum.
- Compare and contrast bright-line emission spectra with dark-line
absorption spectra, including the mechanism for their production
according to the Bohr model of the atom.

Instructions: This reading provides an overview of the material we
will cover in Unit 5. Read it carefully, but please don’t think
that you have to fix every single fact into your memory. What you
should strive for is to be sure that it makes sense to you as you
are reading it and that when you are finished you can briefly
summarize the main points of the reading. You should read this both
as you start and after you have finished working your way through
the unit.
Reading this article should take approximately 45 minutes.

Reading: The University of Tennessee, Knoxville’s Department of
Physics and Astronomy: “Atoms and Molecules”
Link: The University of Tennessee, Knoxville’s Department of Physics
and Astronomy: “Atoms and
Molecules”
(HTML)

Instructions: This article discusses the constituents of atoms and
introduces the concept of isotopes.

Reading this article should take approximately 5 minutes.

Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This article discusses the alpha scattering
experiment Rutherford used in developing his nuclear model of the
atom. Please read it carefully and make sure you understand how the
data supports the model.
Reading this article should take approximately 15 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This video discusses the people who developed various
models of the atom.
Watching this video should take less than 5 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Reading: The University of Tennessee, Knoxville’s Department of
Physics and Astronomy: “The Bohr Model”
Link: The University of Tennessee, Knoxville’s Department of Physics
and Astronomy: “The Bohr
Model”
(HTML)

Instructions: This article introduces you to the Bohr model and the
allowed energy levels of the atom. You should come away with the
distinction between quantized energy levels and continuously allowed
energies.

Reading this article should take approximately 15 minutes.

Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: At this link, you can click on an element in the
table, and information on that element will appear.
Reviewing this information should take approximately 10 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This is an animation that shows how an electric field
affects the three types of radiation and determines their charges.
Watching this video should take less than 5 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This is a Java applet that discusses and illustrates
half-life. It provides animations for the decay in real time of
several short half-fife isotopes. Try this for several different
isotopes. Be sure to scroll down to view the graph as time
elapses.
Studying this resource should take approximately 15 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This article is a brief description of the
contributions of Maxwell and Hertz to our understanding of
electromagnetic radiation.
Reading this article should take approximately 10 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.4.2 The Electromagnetic Spectrum
- Reading: The University of Tennessee, Knoxville’s Department of
Physics and Astronomy: “The Electromagnetic Spectrum”
Link: The University of Tennessee, Knoxville’s Department of Physics
and Astronomy: “The Electromagnetic
Spectrum”
(HTML)

Instructions: This article introduces the various regions of the
electromagnetic spectrum including the colors of the visible
spectrum.
Reading this article should take approximately 10 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This article gives a brief description of the three
types of spectra and the way in which they are produced.
Reading this article should take approximately 10 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This video is mostly about emission spectra and shows
the spectra of several elements.

Watching this video should take approximately 5 minutes.

Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Web Media: The University of Tennessee, Knoxville’s Department of
Physics and Astronomy: “The Solar Spectrum”
Link: The University of Tennessee, Knoxville’s Department of Physics
and Astronomy: “The Solar
Spectrum”
(HTML)

Instructions: This article illustrates the dark-line spectrum of
the sun. It also illustrates the wavelength distributions of a
hotter and a cooler star relative to the sun. This explains why the
surface temperature of a star determines its color.

Reading this article should take approximately 15 minutes.

Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.5.2 Atomic Spectra and the Bohr Model of the Atom
- Reading: The University of Tennessee, Knoxville’s Department of
Physics and Astronomy: “Atomic Absorption and Emission Spectra”
Link: The University of Tennessee, Knoxville’s Department of Physics
and Astronomy: “Atomic Absorption and Emission
Spectra”
(HTML)

Instructions: This article goes over the types of spectra,
discussing the spectrum of hydrogen in some detail.
Reading this article should take approximately 15 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: This article provides a brief history of our models
of light and other types of electromagnetic radiation. It will
introduce you to the strange concept that light sometimes behaves as
if it were a wave and sometimes as if it were a stream of particles,
even though these two models are logically incompatible with one
another. Scientists use one or the other depending on which is most
helpful in their particular application. In most applications in
astronomy, it is easiest to think of light as a wave.
Reading this article should take approximately 15 minutes.
Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

Instructions: When you have finished the entire unit, please
complete this assessment without referring to the readings. When
you are finished with the assessment, you can check your answers
against the Saylor Foundation’s “Unit 5 Assessment – Answer
Key” (PDF).